Rotary compressors and like rotary machines



Dec. 4, 1962 J. w. MARSHALL 3,066,851

ROTARY COMPRESSORS AND LIKE ROTARY MACHINES Filed June 30, 1959 3 Sheets-Sheet l wmmzzm W AW ttorneyg Dec. 4, 1962 J. w. MARSHALL 3,066,851

ROTARY COMPRESSORS AND LIKE ROTARY MACHINES Filed June 30, 1959 WWW A Home Dec. 4, 1962 J. w. MARSHALL ROTARY COMPRESSORS AND LIKE ROTARY MACHINES Filed June 50, 1959 3 Sheets-Shet 3 l i. and is iiflhdflhl Fatented Dec, l, i952 lice 3,366,851 NOTARY QQMPREEBSGRS AND LIKE RUTARY MACHlNES John Wilmott Marshall, Greeniawns, 19 Eastlield Road, lioyston, Harts, England Filed lune 3d, N59, Ser. No. 8233M Claims priority, application Great Britain July 3, 1953 24 Qlaims. (Qt. 23il-l5tl) This invention relates to rotary machines operating with a fluid medium, being applicable primarily to rotary compressors but also having application to other rotary machines such as pumps, rotary engines and fluid motors. More specifically, the invention is concerned with rotary machines of the type in which a pair of interengaging rotors rotate in opposite directions inside a casing and a fluid medium travels round from a casing inlet to a casing outlet between the rotors and the walls of the casing.

According to the present invention, there is provided a rotary compressor or like rotary machine comprising a casing enclosing a rotor chamber, a male rotor and a smaller female rotor mounted for rotation in the rotor chamber in opposite directions and arranged so that each continually maintains close running clearance with the other and with the casing wall, the male rotor having a plurality of lobes which fit into corresponding cavities in the female rotor during rotation, high and low pressure connections to the casing for gaseous fluid from one to the other of which fluid travels round between the rotors and the casing walls as the rotors rotate, and flow-controlling means the high pressure side of the rotor chamber operable to alter the point in the rotational cycle at which at least each moving fluid space or cell associated with the male rotor makes communication with the high pressure connection thereby to alter the pressure reached in the high pressure side of the chamber.

Such an arrangement rovides a compressor capable of delivering oil-free air and having provision for at least partial internal unloading.

In one a rangernent of compressor, the flow-controlling means may comprise a member located at the side of the high ressure outlet connection nearer the male rotor and movable toward and away from the cylinder of revolution traced out by the female rotor whereby said memher is eiiective to close and open a gap between the casing wall and the circumference of said cylinder. The movable member thereby can provide a measure of pressure variation and act as an unloader.

In another arrangement of compressor, the flow-controlling means may comprise a rotary valving arrangement at the high pressure outlet connection which is adjustable to vary progressively the timing of the opening of communication between the rotor chamber and the outlet tract beyond the valve. The rotary valve provision af ords greater facility for the progressive variation of internal compression over a substantial range of delivery pressures.

Such a rotary valving arrangement can be in an outlet from the periphery of the casing in which flow is at rightangles to the rotor axes, or it can be at the end of the casing with the delivery flow axial.

In the preferred construction, the male and female rotors have two lobes and cavities respectively and rotate at the same speed. In the case where a rotary valve is provided this can be arranged to rotate at the speed of the rotors.

The above and other features of the invention will be apparent in the following description, given by way of example, of various rotary air compressor constructions embodying the invention, reference being had to the accompanying diagrammatic drawings. In the drawings:

FIGURE 1 is a cross section through a first compressor construction,

FIGURE 2 is a section on the line Z2 of FIGURE 1, showing the male rotor with its lobes in the horizontal position,

FIGURE 3 is a cross section through a second con struction,

FEGURE 4 is a cross section through a construction similar to that of FIGURE 3 but showing another form of the rotors and with a different position of the moving parts, and

FIGURE 5 to 10 are a series of similar cross sections through further constructions.

in the description that now follows parts in different embodiments that perform the same functions are given the same reference numerals.

Referring firstly to FIGURES l and 2, the rotary air compressor here shown consists primarily of a casing 11 and interengaging male and female rotor l2, 13 within the casing. The casing internal configuration is based on the shape aiforded by two parallel imaginary intersecting cylinders of different sizes, the larger and smaller cylinders corresponding respectively to the solids of revolution traced by the male and female rotors. At one side or" the casing is an inlet 14 and at the other side an outlet 15.

The male rotor 12 consists of a cylindrical hub 16 carrying two diametrically-opposed lobes 1'7 with substantially part-circular profiles 18. The female rotor 13 has basically the form of a cylinder with a pair of diametrically-opposed part-cylindrical cavities 19 which receive the lobes 17 on the male rotor as the two rotors rotate. The rotors turn in opposite directions as indicated by the arrows 20 at the same revolution rate and their dimensions and configurations are such that each maintains a close running clearance both with the internal Wall of the casing and with the other rotor; the clearance is no greater than is necessary to obtain frictionless running and is kept small enough to restrict air leakage as far as possible.

The rotors have shafts 23, 24, which are intercoupled by meshing gears 25, 26 disposed in a gear housing 27 external to the rotor casing, and one shaft 23 has an extension for coupling to a driving motor or engine. Since the speed of revolution of the two rotors is the same, the two gears 25, 26 can be the same which is a convenience in manufacture.

As the rotors turn, air entering at the inlet 14 is trapped in the spaces between each rotor and the Walls 21, 22 of the casing and is carried round to the outlet 15 and discharged. In order to enable the maximum amount of air to enter the machine with the minimum restriction of its flow, it is desirable to have the inlet 14 as large as practicable. The inlet It a could be even larger than is shown in the drawing, for example extending up to the position indicated by the broken lines at 2-8, but it must be borne in mind that increase in the size of the inlet is limited by the essential need for the rotors to maintain proper isolation of the inlet from the outlet of the machine.

Since the amount of air moved by the male rotor 12 is ordinarily greater than that moved by the female rotor 13, it may be an advantage in some machines to incline the outlet 15 so that the larger air quantity discharged by the male rotor has to turn through a smaller angle as it enters the outlet than does the air delivered by the female rotor. in FIGURE 1, the inclination of the outlet 15 is indicated by the angle between the axis of the outlet and a plane parallel to that containing the rotor axes, this particular angle being shown less than a rightangle.

With regard to the construction of the male rotor 12, one convenient method of making this is to secure two pieces of tubing to opposite sides of the central hub l6, such as by bolting as indicated at 29. Standard tubing can be used for this purpose providing that it is given an appropriate external finish to achieve the tolerance involved in establishing the desired close running clearance. To strengthen the male rotor 12 a flange 3b can be provided on the hub or shaft at one or both ends of the rotor, as shown in FIGURE 2. Such flange or flanges could be used in attaching the tube-pieces to the rotor hub. As shown, the tube-pieces extend past the flange fill up to the end wall 31 of the casing 11, but other arrangements are possible and in particular the flanges could overlie the ends of the tubes. It is then best to employ circular flanges which rotate in corresponding circular recesses in the end walls of the casing so that they do not foul the other rotor. Alternatively, the female rotor 13 can have circular end flanges running in recesses in the end walls of the casing. An especial advantage of such flanges is that they materially assist the end sealing of the rotor to which they are applied.

With rotors of the configuration described, the female rotor 13 would foul the male rotor 12 if the surfaces of the cavities 19 of the female rotor met the cylindrical peripheral surfaces 32 in sharp edges. Accordingly, the four sharp tips of the female rotor at these points are removed. By providing flats 2 3 of correct design at these tips, two rotors are obtained which revolve against one another without contact while maintaining the proper running clearance at all points, and it is not necessary to machine pieces out of the male rotor tubes to accommodate the female rotor tips. Also, the female rotor shape is improved in that there are no sharp tips to break away and air noise is lessened as the air is not travelling across sharp rotor edges.

Considering now especially FIGURE 1, it will be seen that if the upper part of the wall ll of the casing 11 is carried round to the point 34 lying substantially on the circumference of the cylinder traced out by the female rotor 13, then for part of each half-revolution of the rotors air entrapped by the male rotor 2.2 will be contained in a space bounded by the male and female rotors and the wall 2-1, which space is progressively decreasing in volume and has for the time being no communication with the outlet 15. The air in this space is therefore compressed. FIGURE 1 shows the rotors in the position where air in the space 35 would be still being compressed but with maximum compression almost reached because after a small amount of further rotation of the female rotor 13 the way from the space 35 to the outlet would be open past the point 34. However, with the wall 21 permanently extended to this position 34 the amount of compression in the machine would be constant.

Alternatively, if the wall 21 does not extend to a point on the circumference of the cylinder traced by the female rotor, but is stopped short to provide a relieving gap, there is communication between the space 35 and the outlet regardless of the position of the female rotor 13, so that no useful compression occurs but only a degree of throttling of the air passing into the outlet through the p- The present arrangement enables adjustment of the machine from operation with internal compression to operation with no internal compression, and this adjustment may be effected while the machine is running. A spring-loaded plate-like member 36 extending across the internal width of the machine is disposed in a guiding recess 37 at one side of the outlet 15 so as to be able to slide up and down like a plunger in the recess in a direction substantially parallel to the axis of the outlet. The lower end face 38 of this plunger plate 36 forms, in effect, a movable part of the wall 21 of the casing ill. When the plunger plate 36 is in the position shown its edge 39 lies substantially at the circumference of the circle traced by the female rotor 13 so that maximum air compression takes place in the machine. When the plunger plate is retracted to the position shown in broken line at ill, a relieving gap 41 is provided and no compression occurs. To ensure that the edge of the plunger plate cannot foul the female rotor its inward movement toward the rotor is positively limited by engagement of a head 41 on the plate with a shoulder 52 on the casing.

The provision for compression variation and internal unloading of the machine which is thus afforded can be employed in a number of ways. The plunger plate can be arranged for adjustment by hand through a suitable control extending to the exterior of the casing. Alternatively, the plunger plate can be automatically adjusted in accordance with the pressure in the outlet tract, or the pressure at some service or apparatus which the machine is supplying, for example through the intermediary of a hydraulic relay.

As will be appreciated, the maximum degree of compression for which such a machine is designed can be selected by appropriate choice of the point around the circumference of the cylinder traced by the female rotor at which the edge 39 of the plunger plate lies when in its inward position. Thus, in FIGURE 1 a smaller amount of compression would be obtained by constructing the machine with a thicker plunger plate such as that indicated in dotted line at 43, because each trailing tip of the female rotor would clear the edge of the plunger plate at an earlier point in the rotation.

While the arrangement of FIGURES l and 2 provides a measure of internal pressure variation and affords the valuable facility of internal unloading of the rotary compressor, there is no provision for compression of the air moved by the female rotor. This further provision is found in the arrangement now to be described with reference to FIGURES 3 and 4, which gives greater facility for the progressive variation of compression over a comparatively wide range of valves.

In FIGURES 3 and 4 there is no sliding plunger plate but instead the outlet 15 contains a rotary valve 44. This valve rotates in the direction of the arrow 45 about an axis parallel to the rotor axes and at the same rotational speed as the rotors, being driven by a third gear meshing with the gear on the shaft of the female rotor 13. This third gear (not shown) can be the same as the other two previously mentioned. The valve has a throughway 46 which passes through register with the outlet channel once during each halfirevolution.

The valve 44 runs in a ported sleeve 47 which does not rotate with the valve but can be adjusted angularly in the outlet 15 by means of an arm 43. No actual contact takes place between the valve and the sleeve but there i a close running clearance both between the valve and the sleeve and between the valve ends and the end faces of the stator casing.

It will be seen that as the valve rotates there are periods when the rotor chamber communicates with the outlet tract and periods when this communication is closed by the valve, and the timing of the opening and closing of this communication in terms of rotor rotation is determined by the setting of the sleeve 47. If, at the time when the valve opens to release air from the rotor chamber to the outlet tract, the space 35 in the rotor chamber bounded by the two rotors and the casing walls has not begun to decrease significantly in volume then there is no internal compression. If, however, the opening of the valve is retarded beyond this point then there will be compression to a degree depending on the amount of the retardation.

FIGURE 3 shows a high pressure setting of the machine in which the valve 44 is about to open as its throughway 46 begins to register with the non-rotary port 4 9 in the sleeve .7. At this point the space 35 in the rotor chamber has already been reduced to a comparatively small volume. In FIGURE 4 the sleeve 47 has been adjusted angularly to a low pressure setting; again the valve 44 is about to open as its throughway begins to register with the port 49, but the volume 35 in the rotor chamber has not yet been reduced to any very great extent.

An important feature of this construction is that the wall of the casing is not brought round to the circumference of the cylinder traced out by the female rotor-but there is a permanent gap as indicated at This brings the air nasscs moved by the male and female r tors into continuous communication durin compression so that both are compressec together. The optimum width for this gap depends on vari us desi n factors including rotational speed and is found empirically. if the gap is too wide there will be too large a residual volume of compressed air flowing back into the rotor chamber after each delivery, whereas if it is too small equalization of pressure in the two air cells will not be adequate.

The ports in the sleeve 47 are provided at intervals with sealing strips 51 which extend parallel to the axis of rotation of the valve. These are necessary to prevent leakage circumferentially around the sleeve through the ports which would upset the valve timing. Five sealing strips are shown in the embodiment illustrated but more or less may be required depending on the design of particular machines.

As in the case of the plunger plate of the first embodiment, the sleeve of the rotary valve can be adjusted manually, or automatically in response to pressure on the outlet side of the machine. When a machine is delivering air to an outlet pressure which is less than the maximum internal pressure of which the machine is capable, it can be a source of inefiiciency to compress the air in the machine to a higher pressure than is necessary. Accordingly, an automatic control responsive to the outlet pressure may be coupled to the arm 43 of the sleeve 47 to keep the sleeve adjusted so that the pressure to which the air is internally compressed in the machine is substantially the same as the outlet tract pressure, rising when the outlet pressure rises and falling when it falls. One simple way of adjusting the sleeve 47 automatically is illustrated schematically in FIGURE 3. The sleeve 47 is adjusted by sliding movement of a rod iill having rack teeth 192 that engage with cooperating teeth 103 on the sleeve. The rod 161 extends through a slideway 104 and emerges at its ends into a pair of opposed cylinders 1425, Hi6. Pistons N7, 133 on the ends of the rod M31 work in the cylinders 1&5, res respectively. The piston 1E7 is acted on 'by a loading spring 1%, while the piston Trill: is subjected to the pressure the compressor outlet tract llil through a pipe lift connecting the cylinder res with the outlet tract. As the pressure in the outlet tract increases the piston 16?, res and the rod Hill are forced across toward the right, as viewed in the drawing, against the action of the loading spring Hi9, thereby progressively adjusting the sleeve 47, the reverse movement takes place when the pressure in the outlet tract falls.

It will be notice that, while the male rotor 12 in FIG- URE 3 is of the same general construction as that in FIG- URES l and 2, an alternative form of male rotor is shown in FIGURE 4 which is of one piece cast construction appropriately machined. With this cast construction, the tips or" the female rotor if desired, be curved instead of being provided with the aforementioned flats 33, this necessitating the provisions of radii also on the male rotor where the tips engage it at the roots of its lobes. In both FIG- URES 3 and 4 the rotors are shown with lightening holes. Labyrinth grooves 52 are provided in the outer extreme surfaces of the lobes of the male rotor 12 to improve sealing, and can also be furnished in the female rotor 13 and in the rotary valve 4-4 if desired.

The remaining embodiments of FIGURES 5 to 10 illustrate another way of achieving rotary valving of the outlet air which involves the delivery of the air axially through the end of the casing. A delivery port 53 is provided in the end wall of the casing, and as the rotors rotate there come in turn into, register with this stationary port 53 two rotary ports 54- formed at diametrically-opposed positions in an endplate provided on one or other of the rotors. In FIGURES 5 and 6 the female rotor 13 has generally circular endplates 55 and the rotary ports 54 are formed in one of these. The end plates as shown are secured to the rotor by four bolts but any other suitable means of attachment may be employed. in FTGURES 7 and 8 end plates 57 are secured to the male rotor 12, again by means of four bolts 58, and the two ports 54 are provided in one of these.

As will be understood, the angular dispositions and sizes of these stationary and rotating ports determine the degree of compression achieved in the machine. In FIGURES 5 and 6, in order to obtain a high degree of compression before release of the air to the outlet tract each rotary port 54 does not begin to come into register with the stationary port 53 until an end plate portion 59 leading it has passed the stationary port. The air in the space 35 as shown in FIGURE 5 is accordingly compressed into the much smaller volume of FEGURE 6 which shows the ports 54, 53 beginning to come into register. If the stationary port 53 were extended to the position shown in dotted line at 6% and the portion 59 of the endplate were removed, no internal compression of the charge would take place and the machine would act as pure displacement blower. Similar considerations ply in the operation or" the arrangements of FIG 7 and 8.

By making the port 53 long in the circumferential direction, and providing in the outlet tract external to the end wall of the casing and against the ported part of the casing wall an angularly-adjustable shutter plate that is also ported, the effective length of the port 53 can be made variable as desired. The compression in the machine is then controllable by adjustment of the shutter plate, which as before may be automatic in response to pressur on the outlet side of the machine. In this arrangement it will ordinarily be necessary to provide sealing strips radially across the port 53 to prevent leakage, the port being then in effect a series of radial slots.

Sealing ribs 61 of this kind are shown in FIGURES 7 and 8 across the rotary ports 54-, the purpose of these being to prevent leakage from the delivery port 53 to the inlet 14 which would otherwise occur for example with the parts in the relative positions shown in FIGURE 8.

With provision for reducing the inte nal compression of the machine, to no compression if required, an unloading facility is afforded which greatly reduces the power absorbed by the machine when there is no call for delivery of compressed air. if in addition a lay-pass port or ports are provided, either in the periphery of the rotor casing or in one or both of the end walls, which are tuicovered in the unloaded condition and direct the air charge displaced by the rotors back to c inlet, very little power will be absor .d at all in run mg the machine unloaded. The mechanical eiliciency is very high since there is no frictional contact at the rotors.

For equalizing the pressures in the separate bodies of air moved by the male and female rotors. during com pression, three different arrangements are shown Fl URES 5, 6 and 8. in FIGURE 5, for example, a duct 62 is provided in the casing wall. If intercommunication between these separate hodies of air is established in this 'way at the commencement of compression this will take place progressively and smoothly in the air volumes of both rotors. If such intercommunication is not established, it will be seen that the volume of air moved by the female rotor will remain uncompressed until that moved by the male rotor has been compressed to a high degree, so that when the two volumes finally mingle there will be a considerable shock wave developed.

in FIGURE 8 pressure equalization is achieved through a channel 63 in the inner wall of the casing, while in FIGURE 6 the casing wall is set back to give a gap as indicated at 64. In the arrangement of FlGURE 6 communication between the air volumes will begin later in the cycle but well before delivery is reached. This tails some loss in efficiency but not so enmuch as when no T7 pre-compression of the female rotor charge takes place at all.

Like the gap Sti in the embodiment of FIGURES 3 and 4, the passages or ducts establishing such intercommunication must be kept as small in volume as possible because they represent a loss in clearance volume; that is to say the air in these passages is uselessly compressed to outlet pressure and then allowed to expand again at thenext cycle.

As in the case of the end flanges described in connection with the embodiment of FIGURES l and 2, the end plates 55 or 57 of the arrangements of FIGURES 5 to 8, on whichever rotor they may be, rotate in circular recesses in the end walls of the casing, there being no contact but a close running clearance between the end plates and the surfaces of the recesses. By providing labyrinth grooves both in the peripheral and radial faces of the end plates improved scaling is obtained at the rotor ends. There may, in some applications, be advantage in employing the arrangement of FEGURE 7 or 8 rather than that of FIGURE 5 or 6, as the delivery port can be larger and the improved end sealing is aiforded to the larger rotor.

FIGURES 9 and 10 show multiple arrangements. In FIGURE 9, there is shown an arrangement in which two female rotors l3 cooperate with one male rotor 12 having twin lobes. There are two air inlets 14, and two clelivery ports 53 in the end wall of the casing controlled by two ports 54 in an end plate on the male rotor. This arrangement delivers four charges of air per revolution of the machine, instead of two, but the pulsation in the out let is the same as before because two deliveries always occur simultaneously.

In FIGURE 10, the male rotor 12 has three lobes and cooperates with three female rotors 13 disposed equiangularly around it. There are three air inlets 14, and three delivery ports 53 in the casing end wall controlled by three rotary ports 54 in an endplate on the male rotor. Nine air changes are delivered for revolution three deliveries taking place simultaneously at each third of a revolution.

Other arrangements are clearly possible, and it is within the scope of the invention to provide a male rotor and cooperating female rotor or rotors in which the number of lobes on the male is different from the number of cavities in the female and the rotors rotate at dilferent speeds.

In the constructions above in which delivery is through the end wall of the casing, there may be delivery and rotary valving arrangements at one or both ends of the casing as desired.

Providing a wide inlet port has been mentioned previously for giving easy passage of air into the machine, and for the same reason the inlet can with advantage be inclined as shown in the constructions of FIGURES 5 to 9. Also it may, in some applications, be advantageous to direct the inlet port so that both sides of it extend to the cylinder of revolution traced out by the female rotor. Thus in FIGURE 10, if the wall 7% of the inlet 14 is moved to the dotted position shown at 71, the gap 72 between the inner edge of the inlet and the female rotor at this side can be close.

Machines of the kind described above are especially suited for use as air compressors, boosters, superchargers and the like in circumstances where the delivery is required to be oil free. Since there is no frictional contact between the moving parts in the internal chambers and passages but everywhere close running clearances, no internal lubrication is required.

The arrangements described are also applicable to fluid motors and rotary engines, in which case the directions of flow and of rotation are reversed with the outlets becoming the inlets and the inlets the exhaust.

It will be appreciated that many modifications are possible without departing from the scope of the invention. For example, while the rotary valve of FIGURES 3 and 4 is described herein as driven through a pair of gears from the female rotor shaft at the same speed as the rotors, it could be driven through a train of gears and/ or designed to run at a different speed. Where the possibility of labyrinth sealing grooves in the moving parts has been mentioned, such grooves could instead be provided in the casing walls and/or bores of the stator, especially around the female rotor.

I claim:

1. A rotary compressor comprising a casing with peripheral and end walls enclosing a rotor chamber, a male rotor and a smaller female rotor mounted for rotation in the rotor chamber about parallel axes at the same speed in opposite directions and out of contact with one another each rotor continually maintaining close running clearance with the other and with the casing walls and thereby separating the rotor chamber into high and I low pressure variable volumes at oposite sides of the rotor chamber that are kept out of substantially all di rect communication with one another by the presence of the rotors, the male rotor having a hub portion and a plurality of lobes that are each wholly of substantially part-cylindrical form which lobes enter into an equal number of smaller-sized corresponding cavities of substantially part-cylindrical form in the female rotor during rotation, the cylinder diameter of each female cavity being larger than the part-circle diameter of each male lobe, gaseous fluid inlet and outlet connections on the casing communicating respectively with the low and high pressure volumes of the rotor chamber and from one to the other of which fluid travels round in moving fluid spaces defined between the rotors and the casing walls as the rotors rotate, and adjustable flow-controlling means at the high pressure volume side of the rotor chamber operable to alter the point during rotation at which at least each moving fluid space associated with the male rotor makes communication with the outlet connection thereby to alter the pressure volume reached in the high pressure of the chamber.

2. A rotary compressor as claimed in claim 1, wherein the flow-controlling means comprises a member located at a side of the outlet connection nearer the male rotor and movable toward and away from a cylinder of revolution traced out by the female rotor whereby said member is effective to close and open a gap between the casing wall and the circumference of said cylinder.

3. A rotary compressor as claimed in claim 1, wherein the flow-controlling means comprises a rotary outlet valve which is adjustable to vary progressively the timing of opening of communication between the rotor chamber and an outlet tract beyond the valve.

4. A rotary compressor as claimed in claim 3, wherein the male and female rotors have two lobes and cavities respectively;

5. A rotary compressor as claimed in claim 4 wherein compressor delivery through the outlet connection is from the casing peripheral wall and in a direction substantially at right angles to the rotor axes, and the rotary valve is disposed in the outlet connection to rotate about an axis parallel to the rotor axes and at right angles to the direction of flow therethrough.

6. A rotary compressor as claimed in claim 5, wherein the rotary valve comprises a valve member which rotates continuously in a ported sleeve that is non-rotary but angularly adjustable.

7. A rotary compressor as claimed in claim 6, wherein the valve member is arranged to rotate at the same speed as the rotors.

8. A rotary compressor as claimed in claim 7, wherein the valve member has a throughway for the compressor delivery at right angles to its axis of rotation.

9. A rotary compressor as claimed in claim 8 wherein at circumferential intervals the valve sleeve ports have sealing strips extending across them in the direction parallel to the axis of rotation.

aoeasel 10. A rotary compressor as claimed in claim 1, wherein one rotor has circular radial flanges at both ends which fit with a close running clearance in corresponding circular recesses in the casing end walls so as not to foul the other rotor.

11. A rotary compressor as claimed in claim 10, wherein the flanges have labyrinth sealing grooves in their surfaces next the surfaces of the casing end wall recesses in which they run.

12. A rotary compressor as claimed in claim 1 wherein at least one pressure-equalizing passage is provided to place bodies of fluid simultaneously moved respectively by the male and female rotors in communication with one another during at least the later part of the period when the fluid moved by the male rotor is being compressed and before delivery commences.

13. A rotary compressor as claimed in claim 12 Wherein the pressure-equalizing passage is provided by a gap left between the peripheral wall of the casing and the cylinder of revolution traced by the female rotor.

14. A rotary compressor as claimed in claim 1 wherein the male rotor has lobes each having a circular profile that intersects a cylindrical rotor hub, and the female rotor is a cylinder with cavities of part-circular profile.

15. A rotary compressor as claimed in claim 14 wherein the male rotor comprises a hub to which are secured lengths of tube forming the lobes.

16. A rotary compressor as claimed in claim 15, where its cavity surfaces meet the cylindrical periphery the female rotor has tips that are formed with flats such that the two rotors have a close running clearance between them in all positions, the male rotor lobes being of constant radius throughout their circular profiles.

17. A rotary compressor comprising a casing with peripheral and end Walls enclosing a rotor chamber, a male rotor and a smaller diameter female rotor mounted for rotation in the rotor chamber about parallel axes at the same speed in opposite directions and out of contact with each other, each rotor continually maintaining close running clearance with the other and with the casing walls and thereby separating the rotor chamber into high and low pressure variable volumes at opposite sides of the rotor chamber that are kept out of substantially all direct communication by the presence of the rotors, the male rotor having a plurality of lobes each having the shape of a major part of a cylinder with the cylinder axes extending straight and parallel to the rotor axis, which lobes enter into corresponding cavities in the female rotor during rotation, gaseous fluid inlet and outlet connections on the casing communicating respectively with the low and high pressure volumes of the rotor chamber and from one to the other of which fluid travels round in moving fluid spaces defined between the rotors and the casing Walls as the rotors rotate, delivery of high pressure fluid to the outlet connection taking place through an end wall of the casing provided with at least one delivery port positioned to communicate with the high pressure volume side of the rotor chamber, and rotary valve means controlling delivery from the high pressure volume side of the rotor chamber to the outlet connection, said rotary valve means including a rotor end plate having in it at least one valve port, which end plate maintains close running clearance with said casing end wall and opens and closes the delivery port therein as its own port moves into and out of register therewith during rotation of said end plate.

18. A rotary compressor as claimed in claim 17, wherein the ported end plate is on the female rotor.

19. A rotary compressor as claimed in claim 17, wherein the ported end plate is on the male rotor.

20. A rotary compressor as claimed in claim 19, wherein the end plate on the male rotor has two parts each divided up into a series of radial slots by spaced radial sealing strips.

21. A rotary compressor comprising a casing with pc- 10 ripheral and end walls enclosing a rotor chamber, a male rotor and a smaller diameter female rotor mounted for rotation in the rotor chamber about parallel axes at the same speed in opposite directions and out of contact with one another, each rotor continually maintaining close running clearance with the other and with the casing walls and thereby separating the rotor chamber into high and low pressure variable volumes at opposite sides of the rotor chamber that are kept out of substantially all direct communication with one another by the presence of the rotors, the male rotor having a hub portion and a plurality of lobes extending straight and parallel to its axis and each wholly of part-cylindrical form which lobes enter into an equal number of part-cylindrical cavities in the female rotor during rotation the diameter in respect of the cylindrical part of each female cavity being larger than the diameter in respect of the cylindrical part of each male lobe, gaseous fluid inlet and outlet connections on the casing communicating respectively with the low and high pressure volumes of the rotor chamber and from one to the other of which fluid travels round in moving fluid spaces defined between the rotors and the casing walls as the rotors rotate, and automatically-reguable flow-controlling means at the high pressure volume side of the rotor chamber operable in accordance with variations in pressure in an outlet tract beyond the outlet connection to alter the point during rotation at which a least each moving fluid space associated with the mae rotor makes communication with the outlet connection.

22. A rotary compressor comprising a casing with peripheral and end walls enclosing a rotor chamber, a male rotor and a smaller diameter female rotor mounted for rotation in the rotor chamber about parallel axes at the same speed in opposite directions and out of contact with one another, each rotor continually maintaining close running clearance with the other and with the casing walls and thereby separating the rotor chamber into high and low pressure variable volumes at opposite sides of the rotor chamber that are kept out of substantially all direct communication with one another by the presence of the rotors, the male rotor having two lobes extending straight and parallel to its axis and each of cylindrical shape that intersects a cylindrical male rotor hub, and the female rotor being a cylinder with two cavities of part-circular profile into whirh the male rotor lobes enter during rotation the cylinder diameter of each female cavity being larger than the circular profile diameter of each male lobe, and gaseous fluid inlet and outlet connections on the casing cornmunicating respectively with the low and high pres ure volumes of the rotor chamber and from one to the other of which fluid travels round in moving fluid spaces defined between the rotors and the casing Walls as the rotors rotate.

23. A rotary compressor as claimed in claim 22 wherein at least one of the rotors has labyrinth sealing grooves at its surface extremities where it is in close running clearance with the casing.

24. A rotary compressor as claimed in claim 22 Wherein one male rotor co-operates with a plurality of female rotors.

References Cited in the file of this patent UNITED STATES PATENTS:

Re. 22,818 Berry Dec. 17, 1946 165,805 Disston July 20, 1875 685,775 Lindsay Nov. 5, 1901 726,969 Motsinger May 5, 1903 1,098,256 Harper Mar. 26, 1914 2,130,054 Whitfield Sept. 13, 1938 2,287,716 Whitfield June 13, 1942 2,580,006 Densham Dec. 25, 1951 (Other references on foiiowing page) 11 UNITED STATES PATENTS Rathman Oct. 27, 1953 Brown Oct. 5, 1954 Mossin Dec. 28, 1954 Ulander Aug. 2, 1955 Tryhorn Nov. 22, 1955 Fawzi Oct. 14, 1958 12 FOREIGN PATENTS Switzerland Sept. 25, 1902 Germany Feb. 9, 1956 Switzerland Nov. 17, 195 2 Germany Aug. 26, 1915 Belgium Dec. 15, 1952 France June 22, 1955 

